Glyphosate formulation

ABSTRACT

A liquid high-strength acqueous glyphosate concentrate comprising butylamine cation and glyphosate anion in the presence of an alcohol ethoxylate adjuvant. A preferred co-surfactant is an alkylpolyglycoside. The composition is stable against phase separation even at high ambient temperatures without the need for structuring agents and/or cationic surfactants.

This invention relates to a glyphosate formulation and in particular toa high-strength aqueous concentrate formulation of glyphosate.

N-phosphonomethylglycine (referred to herein by the common nameglyphosate) is a well-known herbicide, which is generally used as aglyphosate acid anion counterbalanced by a suitable cation.Commercially, trimethylsulphonium and isopropylamine are currently thecommonest cations although sodium, potassium, monoethanolamine andammonium cations are also of interest. Glyphosate can be formulated in awide variety of liquid and solid compositions designed to cover a rangeof commercial applications. This invention concerns liquid concentrateformulations, which are designed to be diluted prior to use. Many suchliquid concentrates are sold commercially, but there are strongcommercial and environmental reasons for seeking to increase theconcentration of glyphosate in the aqueous formulation beyond that whichis commonly available. It is readily apparent that a high-strengthaqueous concentrate formulation provides a given dose of glyphosate in asmaller liquid volume, resulting in significant advantages in terms ofreduced transport, storage and handling costs and reduced and moreconvenient container disposal.

It is well understood that in commercial practice it is necessary toenhance the activity of glyphosate by the use of one or more adjuvants.One commonly used class of adjuvants are surfactants, and many effectiveindividual surfactants or mixed surfactant systems have been publishedin the literature. It is possible to add a desired surfactant separatelyinto a tank mix at the same time that the aqueous glyphosate concentrateis diluted, and the surfactant can thus be omitted from the concentrateand added separately at the tank mix stage. Clearly however the additionof a surfactant at the tank mix stage constitutes an additional stepprior to spraying the herbicide and requires the user to undertakeaccurate measurement of mixing volumes to ensure the correct proportionsin the final product. There is a need therefore for high-strengthglyphosate concentrates in which an effective proportion of a surfactantis “built-in” to the composition. The term “built-in” as used hereinindicates a composition in which the required primary adjuvants arecontained within a physically stable concentrate composition and do nothave to be added during the tank mix stage. This does not of coursepreclude the operator adding further adjuvants during tank mix ifdesired, but there is no necessity for the addition of furtheradjuvants. The difficulties of providing effective high-strengthglyphosate concentrates containing adjuvant systems are considerable,since such concentrates have to be physically stable over extendedstorage at the possible extremes of ambient temperatures likely to beencountered in commercial usage.

One particular stability problem arises when alcohol ethoxylates areused as adjuvants for conventional glyphosate formulations in built-inconcentrates. Although alcohol ethoxylates are good surfactants andeffective adjuvants, there is a tendency for them to separate out fromconcentrated glyphosate solutions at higher temperatures, for exampleabove 50° C. to 60° C. Such compositions, for example compositionscontaining glyphosate in association with a cation such asisopropylamine, trimethylsulphonium, monoethanolamine, potassium, sodiumor ammonium are strong electrolytes, which tend to give rise tocompatibility problems with alcohol ethoxylates. This can lead toproblems when glyphosate concentrates are stored at, or exposed to, hightemperatures, for example by being left in a vehicle in the sun, or inhot climates. One problem caused by separation of the adjuvant is thatthe herbicidal effectiveness of the composition is reduced in thoseparts of the composition where there is a reduced level of adjuvant.There may also be an increased tendency to foaming in those parts of thecomposition where there is an increased level of the adjuvant, becauseof the adjuvant's inherent surfactant properties. Furthermore, onceseparation occurs, it may not be practicable to reincorporate theadjuvant, particularly in high volume containers or storage tanks, whichcan be up to 100 000 litres in volume and which it would be quiteimpractical to agitate to the required extent.

In WO 99/09822 it is proposed to mitigate compatibility problems arisingfrom the use of alcohol ethoxylates in the presence of an agrochemicalelectrolyte such as glyphosate salts by forming a structured (gel)system by means on the interaction of an alkyl glycoside and aco-surfactant. Whilst such a system acts to overcome compatibilityproblems even if phase separation does occur, the co-surfactant willtend to add to the cost of the formulation and it is highly desirable toprovide a system in which phase separation does not occur in the firstplace.

We have now found that the glyphosate when associated with thebutylamine cation can be used in place of the more conventionalglyphosate presentations to provide stable “built-in” concentratecompositions despite the presence of alcohol ethoxylate adjuvants. Wehave found that such compositions are temperature-stable such that theadjuvant phase resists separating out from the composition at up to 40°C. or higher such as 50° C.

According to the present invention there is provided a liquidhigh-strength aqueous glyphosate concentrate comprising butylaminecation and glyphosate anion in the presence of an alcohol ethoxylateadjuvant.

The concentrate is preferably presented as a single phase.

As used herein, the term “high-strength” aqueous glyphosate concentrateindicates a concentrate in which the glyphosate concentration is greaterthan 240 g/l based on glyphosate acid content, for example from 240 to400 g/l. An especially preferred concentration is from 340 to 380 g/lbased on glyphosate acid. It should be noted that, unless otherwisestated, all concentrations of glyphosate are given herein in terms ofthe percentage by weight of glyphosate acid even though the glyphosateanion is balanced by a butylamine cation.

The composition of the present invention comprises butylamine cation andglyphosate anion. Each glyphosate anion will normally be substantiallymatched with one butylamine cation (the monobutylamine salt ofglyphosate), although excess glyphosate anion or butylamine cation maybe used if desired. Alternatively other cationic species, including theconventional isopropylamine, trimethylsulphonium, sodium, potassium,monoethanolamine or ammonium cations, may be present in addition to thebutylamine cation.

The alcohol ethoxylate is preferably a linear or branched chainsaturated or unsaturated aliphatic or aromatic alcohol and can have oneor more hydroxy groups. The alcohol ethoxylate is preferably obtained byethoxylation of a linear or branched chain aliphatic mono alcohol havinga chain length of from 8 to 20 carbon atoms or a mixture of suchalcohols having an average chain length of from 8 to 20 and morepreferably from 10 to 18 carbon atoms. A primary alcohol is preferred.An example of an alcohol ethoxylate for use in the present invention isthat derived from a mixture comprising a primary alcohol containing 13carbon atoms and a primary alcohol containing 15 carbon atoms. The ratioof the C13 alcohol to the C15 alcohol is typically from 30:70 to 70:30and the mixture generally contains both linear and branched alcohols,for example, about 50% by weight of linear alcohols. An example of anethoxylated aromatic alcohol is nonyl-phenol ethoxylate, althoughprimary aliphatic alcohol ethoxylates are generally preferred.

The mean degree of ethoxylation (mean molar ethylene oxide content) ispreferably from 2 to 50 moles of ethylene oxide per mole of alcohol, andespecially from 10 to 20 moles of ethylene oxide per mole of alcohol.The most efficacious degree of ethoxylation can vary somewhat dependingupon the weed species being treated. It is therefore possible either toselect the most efficacious mean degree of ethoxylation for a specifictarget weed or to seek a mean degree of ethoxylation which isefficacious over a broad range of species. In general we have found thateffective treatment over a broad range of species is obtained when themean degree of ethoxylation is from 11 to 18 moles of ethylene oxide permole of alcohol. There may in some instances be an advantage inobtaining a broad species response by using a composition having a broaddistribution of ethylene oxide content around the mean value. Theappropriate mean ethylene oxide content can if desired be obtained bymixing two or more commercially available alcohol ethoxylates havingvarious ethylene oxide contents in the appropriate ratio. This has thedual advantage of enabling a desired mean ethylene oxide content to beachieved precisely and also of ensuring that a broad distribution ofethylene oxide contents is present. Thus for example a mean ethyleneoxide content of 15 moles of ethylene oxide per mole of alcohol can beachieved by mixing the commercially available alcohol ethoxylateSYNPERONIC A11 (SYNPERONIC is a trademark of IMPERIAL CHEMICALINDUSTRIES PLC) which has a mean ethylene oxide content of 11 withSYNPERONIC A20 (which has a mean ethylene oxide content of 20) in theratio 3 to 2.

A number of suitable alcohol ethoxylates are commercially availableincluding for example the SYNPERONIC A series having a range of ethyleneoxide contents (indicated by the number after the “A”) and based on aprimary C₁₃-C₁₅ alcohol containing about 50% by weight linear alcohol,the remainder being mainly mono-branched; CIRRASOL ALN-WF (a mixture ofC16-C18 linear alcohols with a mean ethylene oxide content of 17); BRIJ96 and 98 based on an unsaturated C₁₈ linear alcohol and having a meanethylene oxide content of 10 and 20 respectively; Mergital LM aC₁₂/C₁₄/C₁₆ alcohol ethoxylate (11EO for Mergital LM 11 and 17 EO forMergital LM 17); and RENEX 30 based on a branched C₁₃ alcohol having amean ethylene oxide content of 12.

Preferably the content of the alcohol ethoxylate in the aqueousconcentrate is from about 20 to 250 g/l. In general, the higher theconcentration of the glyphosate present in the composition, the lowerthe concentration of alcohol ethoxylate which can be effectivelybuilt-in to the composition without the risk of encountering stabilityproblems under extreme conditions. The concentration of alcoholethoxylate, which can be effectively built-in to the composition, willalso depend to some extent on any other components of the compositionssuch as the presence of a co-adjuvant. Since it is normally commerciallydesirable for the glyphosate concentration to be relatively high, forexample about 340 to 380 g/l, it is preferred that the alcoholethoxylate concentration is from 20 to 200 g/l and especially from 40 to150 g/l. We have found that concentrations of alcohol ethoxylate withinsuch preferred ranges provide compositions having excellent stability inthe presence of a high concentration of glyphosate, whilst at the sametime containing sufficient alcohol ethoxylate to provide the desiredlevel of bioperformance enhancement. We have found in general thatcompositions of the present invention are able to support a highercontent of alcohol ethoxylate than would be the case for correspondingcompositions containing conventional cations.

Compositions of the present invention may also comprise a furtheradjuvant in addition to the alcohol ethoxylate. Suitably the co-adjuvantfunctions in a different manner from the alcohol ethoxylate to provide acomplementary adjuvancy effect. For example it is preferred that thecompositions of the present invention also comprise an alkylglycoside.The alkylglycoside for use in the present invention can be obtained bythe reaction of alkanols with glucose or other mono- or di- orpolysaccharides. As used herein the term “alkylglycoside” includes analkylmonoglycoside and an alkylpolyglycoside. Preferred alkylglycosidesfor use in the present invention are alkylglucosides obtained by thereaction of glucose with a straight or branched chain alkanol or mixtureof alkanols, for example a mixture of alkanols containing 7 to 18,preferably 7 to 16 carbon atoms for example 8 to 10 carbon atoms. Thenumber of glycose groups per alkyl group in the molecule can vary andalkyl mono- or di- or polyglucose or saccharide derivatives arepossible. Commercial alkylpolyglucosides usually contain a mixture ofderivatives having an average number of glycose groups per alkyl group.Thus alkylglycosides have the general formula (I),

, wherein n is the degree of polymerisation and is typically within therange from 1 to 3, for example from 1 to 2, and R⁵ is a branched orstraight chain alkyl group having from 4 to 18 carbon atoms or-a mixtureof alkyl groups having an average value within the given range. Typicalof alkylglycosides is the product commercially available under the tradenames AL2042 (Imperial Chemical Industries PLC) and AGRIMUL PG2067(Henkel Corp) wherein n is an average of 1.7 and R⁵ is a mixture ofoctyl (45%) and decyl (55%), the product commercially available underthe trade name AGRIMUL PG2069 (Henkel Corp) wherein n is an average of1.6 and R⁵ is a mixture of nonyl (20%), decyl (40%) and undecyl (40%)and the product commercially available under the trade name BEROL AG6202(Akzo Nobel) which is 2-ethyl-1-hexylglycoside.

It is a particular advantage of the alkylglycoside surfactant that it iscompatible with the high ionic-strength electrolyte composition of thepresent invention.

Preferably the content of the alkylglycoside surfactant system in theaqueous concentrate is from 0 to about 250 g/l. The content of thealkylglycoside surfactant is preferably from 20 to 250 g/l andespecially from 40 to 150 g/l. It will be appreciated that the exactchoice of the concentration of alkylglycoside selected will depend tosome extent on the concentration of glyphosate and alcohol ethoxylatepresent in the composition.

A proportion of the alkylglycoside may if desired be replaced by acationic surfactant such as an alkoxylated alkylamine or a quaternarysurfactant and in some circumstances an increase in biological activitycan be observed thereby.

As is conventional practice, an antifoam can be added. Numerousantifoams are known in the art and commercially available antifoamsoperate at very low concentrations (for example less than 5 g/l) andhence do not have a major impact on the loading of the composition.

Other conventional additives such as humectants, activity enhancers(such as inorganic ammonium salts anti-freeze agents, wetters, or otheradditional surfactants can be added if desired. Similarly, additionalwater-soluble herbicides or other agrochemicals such as fungicides andinsecticides can be incorporated if desired.

Co-surfactants acting as structuring agents and/or cationic surfactantssuch as those listed in WO 99/09822 may be added if desired but it is aparticular advantage of the composition of the present invention thatthe composition is stable at relatively high glyphosate concentrationand at relatively high ambient temperature without the need to add suchstructuring agents and/or cationic surfactants. This in turn providesgreater “capacity” in the formulation to accommodate additionaladjuvants that may provide desirable bioperformance enhancement.

When diluted for use, compositions of the present invention are activeagainst a broad range of weed species including monocotyledonous anddicotyledonous species. The compositions are suitably applied directlyto unwanted plants (post-emergence application).

Thus according to a further aspect of the present invention there isprovided a process of severely damaging or killing unwanted plants whichcomprises diluting a concentrated composition of the present inventionand applying to the plants a herbicidally effective amount of a saiddiluted composition.

The rate of application of the composition of the invention will dependon a number of factors including, for example, the identity of theplants whose growth is to be inhibited and whether the compound is to beapplied for foliage or root uptake. As a general guide, however, anapplication rate of from 0.001 to 20 kilograms per hectare is suitablewhile from 0.025 to 10 kilograms per hectare may be preferred.

The compositions of the present invention can be made by mixing thecomponents in the desired proportions. The particular combination ofions in the composition of the present invention can be obtained from arange of different starting materials. The order of addition is notparticularly important. Thus, butylamine can be added to glyphosate acidin the presence of the alcohol ethoxylate, and optionally anyco-adjuvant.

Compositions of the present invention can also be provided in a dilutedand ready-to-use form but is suitably a concentrate. Additionaladjuvants suitable for ready-to-use formulations can also be added e.g.antifreeze, polymers and dyes.

The invention is illustrated by the following Examples in which allparts and percentages are by weight unless otherwise stated.

EXAMPLE 1

A composition was prepared consisting of the monobutylamine salt ofglyphosate at a concentration equivalent of 360 g/l glyphosate acid,AGRIMUL PG2067 (86 g/l of a 70% w/w solution of alkylpolyglycoside inwater) and MERGITAL LM 11 (50 g/l of a 99.7% w/w solution of alcoholethoxylate in water). A homogeneous single-phase composition was formed.The composition was stored respectively at ambient temperature (taken as20° C.), 50° C. and 54° C. for a period of 14 days. No indication ofphase separation was observed.

EXAMPLE 2

The procedure of Example 1 was repeated with a composition consisting ofthe monobutylamine salt of glyphosate at a concentration equivalent of360 g/l glyphosate acid, AGRIMUL PG2067 (115 g/l of a 70% w/w solutionof alkylpolyglycoside in water) and MERGITAL LM 11 (115 g/l of a 99.7%w/w solution of alcohol ethoxylate in water). A homogeneous single phasecomposition was formed. The composition was stored respectively atambient temperature (taken as 20° C.), 50° C. and 54° C. for a period of14 days. No indication of phase separation was observed.

COMPARISON

The procedure of Example 2 above was repeated using the sameconcentrations of alkylpolyglycoside and alcohol ethoxylate except thatthe butylamine salt of glyphosate was replaced respectively by themonoethanolamine salt and the potassium salt of glyphosate at theequivalent concentration of 360 g/l glyphosate acid. Both theethanolamine and potassium compositions underwent phase separation whenstored at ambient temperature for 14 days.

EXAMPLE 3

The procedure of Example 2 was repeated using the same concentrations ofalkylpolyglycoside, alcohol ethoxylate , except that 30 g/l of astructuring agent (2-ethyl-1-hexanol) was added according to theprocedure of WO 99/09822. Whilst the addition of such a structuringagent is unnecessary (in that the corresponding formulation of Example 2was stable without the addition of a structuring agent), the addition ofthe 2-ethyl-1-hexanol had no adverse effect and the composition wasstable when stored at ambient temperature (taken as 20° C.), 50° C. and54° C. for a period of 14 days.

COMPARISON

The procedure of Example 3 was repeated using the same concentrations ofalkylpolyglycoside, alcohol ethoxylate and structuring agent except thatthe butylamine salt of glyphosate was replaced respectively by themonoethanolamine salt and the potassium salt of glyphosate at theequivalent concentration of 360 g/l glyphosate acid. Despite thepresence of structuring agent, both the ethanolamine and potassiumcompositions underwent phase separation when stored at ambienttemperature for 14 days

EXAMPLE 4

The procedure of Example 3 was repeated using the same concentrations ofalkylpolyglycoside, alcohol ethoxylate and structuring agent(2-ethyl-1-hexanol) except that 10 g/l of a cationic surfactant ARQUAD16-29 was added according to the further procedure of WO 99/09822.ARQUAD 16-29 is a 29% by weight solution of hexadecyl trimethyl ammoniumchloride in water. ARQUAD is a trademark of Akzo Nobel. Whilst theaddition of such a structuring agent/cationic surfactant is unnecessary(in that the corresponding formulation of Example 2 was stable withoutthe addition of a structuring agent/cationic surfactant system), theaddition of the 2-ethyl-1-hexanol and cationic surfactant had no adverseeffect and the composition was stable when stored at ambient temperature(taken as 20° C.), 50° C. and 54° C. for a period of 14 days.

COMPARISON

The procedure of Example 4 was repeated using the same concentrations ofalkylpolyglycoside, alcohol ethoxylate, structuring agent and cationicsurfactant except that the butylamine salt of glyphosate was replaced bythe monoethanolamine salt of glyphosate at the equivalent concentrationof 360 g/l glyphosate acid. In the presence of structuring agent andcationic surfactant, the ethanolamine composition remained stable atambient temperature but underwent phase separation when stored at 50° C.for 14 days.

It was found necessary to increase the concentration of2-ethyl-1-hexanol to 50 g/l (in the presence of 10 g/l ARQUAD 16-29)before the ethanolamine composition was stable both at ambienttemperature and 50° C./54° C. Even using these increased proportions ofstructuring agent and cationic surfactant, the potassium salt underwentphase separation at ambient temperature.

1. A liquid high-strength aqueous glyphosate concentrate comprisingbutylamine cation and glyphosate anion in the presence of an alcoholethoxylate adjuvant wherein the glyphosate concentration is greater than240 g/l based on glyphosate acid content.
 2. A concentrate according toclaim 1 wherein the glyphosate concentration is from 240 to 400 g/lbased on glyphosate acid.
 3. A concentrate according to claim 1 whereinthe glyphosate concentration is from 340 to 380 g/l based on glyphosateacid .
 4. A concentrate according to claim 1 wherein the alcoholethoxylate is obtained by ethoxylation of a linear or branched chainaliphatic mono alcohol having a chain length of from 8 to 20 carbonatoms or a mixture of such alcohols having an average chain length offrom 8 to 20 carbon atoms.
 5. A concentrate according to claim 4 whereinthe alcohol ethoxylate is obtained by ethoxylation of a linear orbranched chain aliphatic mono alcohol having a chain length of from 10to 18 carbon atoms or a mixture of such alcohols having an average chainlength of from 10 to 18 carbon atoms.
 6. A concentrate according toclaim 4, wherein the alcohol from which the alcohol ethoxylate isderived is a primary alcohol.
 7. A concentrate according to claim 6wherein he alcohol from which the alcohol ethoxylate is derived is amixture comprising a primary alcohol containing 13 carbon atoms and aprimary alcohol containing 15 carbon atoms.
 8. A concentrate accordingto claim 1, in which the mean degree of ethoxylation is from 2 to 50moles of ethylene oxide per mole of alcohol.
 9. A concentrate accordingto claim 8 in which the mean degree of ethoxylation is from 10 to 20moles of ethylene oxide per mole of alcohol.
 10. A concentrate accordingto claim 8 in which the mean degree of ethoxylation is from 11 to 18moles of ethylene oxide per mole of alcohol.
 11. A concentrate accordingto claim 1, containing from 20 to 250 g/l of alcohol ethoxylate.
 12. Aconcentrate according to claim 3 containing from 20 to 200 g/l ofalcohol ethoxylate.
 13. A concentrate according to claim 12 containingfrom 40 to 150 g/l of alcohol ethoxylate.
 14. A concentrate according toclaim 1, comprising a further adjuvant in addition to the alcoholethoxylate wherein said further adjuvant is an alkylglycoside.
 15. Aconcentrate according to claim 14 wherein the alkylglycoside is obtainedby the reaction of glucose with a straight or branched chain alkanol ormixture of alkanols, for example a mixture of alkanols containing 7 to18 carbon atoms.
 16. A concentrate according to claim 14, wherein thecontent of the alkylglycoside surfactant is from 20 to 250 g/l.
 17. Aconcentrate according to claim 16 wherein the content of thealkylglycoside surfactant is from 40 to 150 g/l.
 18. A process ofseverely damaging or killing unwanted plants which comprises diluting aconcentrate according to any of the preceding claims and applying to theplants a herbicidally effective amount of said diluted concentrate.